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DNV: Addressing methane slip in LNG-burning four-stroke Otto-cycle engines

DNV discusses LNG and methane slip in a Maritime Impact report and elaborates on its role in several projects aiming to minimize methane slip.

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DNV: Addressing methane slip in LNG-burning four-stroke Otto-cycle engines

Classification society DNV on Monday (27 November) released a Maritime Impact report discussing LNG and methane slip and DNV’s role in several initiatives to minimize it. The following is an excerpt from the article: 

LNG offers many benefits as a transitional ship fuel. However, certain engine types have been found to release significant amounts of unburnt methane, a powerful climate gas. DNV is involved in various projects aiming to minimize methane slip.

Methane, the main component of natural gas and LNG, has a global warming potential (GWP) 29.8 times that of carbon dioxide (CO2) over a 100-year timeframe, according to the Intergovernmental Panel on Climate Change (2021). Preventing methane from escaping anywhere along its supply chain is therefore crucial as the world tries to contain the causes of climate change.

New EU regulations increase pressure to reduce methane slip

LNG-fuelled four-stroke Otto-cycle engines, which are often used for gensets on board passenger ships, have been found to release significant amounts of unburnt methane, leading to CO2-equivalent emission values that compromise what is achieved through other carbon reduction efforts. 

The shipping sector will be incorporated into the EU’s Emissions Trading System (ETS) from 2024. This expansion will encompass methane and nitrous oxide emissions starting in 2026. Additionally, the FuelEU Maritime requirements for the GHG intensity of energy utilized on board will come into effect in 2025. Consequently, the shipping industry is keenly interested in addressing methane slip issues.

LNG’s long-term zero emissions potential hinges on methane slip reduction

“Many think of LNG as a transitional fuel only, but it can also be much more than this,” says Hans Eivind Siewers, Segment Director Passenger Ships and RoRo at DNV. “But in order for this fuel to take passenger ships all the way to zero emissions with bio LNG and e-LNG, it is of major importance that we succeed in reducing methane slip.”   

Fabian Kock, Head of Section Environmental Technologies Air at DNV, agrees: “Methane slip is indeed a critical issue for addressing climate change. DNV is actively working with many stakeholders and regulators to find pragmatic solutions to overcome this challenge. In particular we are happy to work closely together with the engine designers to find technical solutions which are safe and feasible to be installed on board of ships.” 

GREEN RAY industry initiative addresses methane slip

One major initiative dedicated to reducing methane slip from LNG ship engines is the EU HORIZON project GREEN RAY (new GeneRation marinE ENgines and Retrofit solutions to Achieve methane abatement flexibilitY). Launched in June 2022 under the leadership of the VTT Technical Research Centre of Finland, it aims to establish sound scientific data about methane slip from four-stroke LNG-fuelled engines by conducting on-board exhaust gas measurements, and to promote the development of methane abatement technologies. 

The project consortium includes the Finnish Meteorological Institute, Shell Global Solutions, Wärtsilä, MSC, CMA Ships, Chantiers de l’Atlantique, DNV and a number of other stakeholders. A report will summarize the findings after the project ends in 2027.

Focus on engine optimization and exhaust gas aftertreatment

The engine manufacturer Wärtsilä has been conducting research and development on engine modifications to radically reduce methane slip, including efforts to optimize engine design and control. VTT researchers studied methane emissions from two Wärtsilä 31DF engines on the AURORA BOTNIA. One used standard configuration, the other tested new combustion. Results show reduced methane emissions and potential for overall emission cuts for the modified engine. 

Shell is developing methane absorption and catalytic conversion technologies for exhaust gas aftertreatment. The role of DNV in the GREEN RAY project will be to witness exhaust gas measurements, verify piping and materials as well as installation, and develop and update its class rules related to emission reduction with the option to introduce a dedicated class notation. Furthermore, DNV will provide know-how and review solution proposals. 

MAN takes a two-pronged approach

There are similar initiatives beyond the GREEN RAY project, as well. MAN Energy Solutions SE has been exploring ways to optimize its own engine technology to minimize methane slip. The company’s R&D into engine optimization is well advanced and integrated into every new four-stroke ship engine MAN delivers, says Dr Mathias Moser, Head of Technology and Exhaust Aftertreatment at MAN Energy Solutions SE. 

“We optimize the mechanical components to minimize crevice volumes in the cylinder and we adapt the compression ratio towards improved combustion,” he explains. “Furthermore, we fine-tune engine control parameters such as injection timing, pilot-fuel amount, supercharge pressure, ignition timing, valve timing and combustion temperature. Most of these improvements can be implemented as retrofits to existing engines, as well. These engine-based measures alone can reduce methane emissions significantly so the updated engines will comply with future, tighter restrictions.”

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Note: DNV’s full Maritime Impact report on ‘Addressing methane slip in LNG-burning four-stroke Otto-cycle engines’ can be found here.

Photo credit: MAN Energy Solutions, Avenir LNG
Published: 6 December, 2023

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Alternative Fuels

Yang Ming orders six LNG dual-fuel, ammonia-ready containerships from Hanwha Ocean

Each of the six new vessels will have a capacity of up to 13,650 TEU and feature LNG dual-fuel propulsion and Ammonia Fuel Ready specifications.

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Yang Ming orders six LNG dual-fuel, ammonia-ready containerships from Hanwha Ocean

Taiwanese shipping firm Yang Ming Marine Transport Corporation (Yang Ming) and South Korean shipbuilder Hanwha Ocean on Wednesday (2 September) signed a shipbuilding contract for six 13,000 TEU class LNG dual-fuel container vessels. 

The contract was signed by Dr. Chuck Tsai, Chairman of Yang Ming, and Mr. Charles Kim, CEO of Hanwha Ocean. The vessels are scheduled for delivery between 2028 and 2029. 

They will complement Yang Ming’s existing fleet of 10,000+ TEU vessels and serve as key vessels on East-West services, with deployment flexibility across trade lanes connecting Asia with the East and West Coasts of North America, South America, and the Mediterranean. 

Each of the six new vessels will have a capacity of up to 13,650 TEU and feature LNG dual-fuel propulsion and Ammonia Fuel Ready specifications.

“As Yang Ming transitions toward net-zero emissions, LNG provides a relatively mature and economically viable alternative fuel solution, capable of reducing greenhouse gas emissions by approximately 20%,” the company said. 

“At the same time, ammonia can serve as a carbon-free fuel by utilising converted LNG storage facilities, while offering relatively lower conversion costs and comparatively well-developed supply chains and infrastructure. The Ammonia Fuel Ready design will therefore provide Yang Ming with greater flexibility in responding to increasingly stringent international regulations on greenhouse gas emissions.”

In addition, the vessels will be equipped with Type B LNG fuel tanks with a design pressure of 1.0 bar to enhance the safety and efficiency of LNG operations, together with a range of energy-saving technologies, including Wind Shields, Rudder Bulbs, Pre-Swirl Stators, and Shore Power Systems. Smart ship technologies and cybersecurity protection features will also be incorporated to enhance operational efficiency, safety, and reliability while effectively reducing fuel consumption and greenhouse gas emissions.

Deliveries under Yang Ming’s next-generation fleet optimization plan commenced earlier this year. By 2030, a total of 24 new vessels are expected to enter service. 

This includes 18 LNG dual-fuel vessels—comprising five 15,500 TEU, seven 16,000 TEU, and the six 13,000 TEU vessels under this contract—alongside six 8,000 TEU methanol dual-fuel-ready ships. 

 

Photo credit: Yang Ming Marine Transport
Published: 4 September, 2026

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Alternative Fuels

LR, China’s MARIC unveil tanker concept ready for three future bunker fuels

Both secured AiP for a new 114,000 DWT product and crude oil tanker designed to accommodate future conversion to LNG, methanol or ammonia.

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LR, China’s MARIC unveil tanker concept ready for three future bunker fuels

Lloyd’s Register (LR) and the Marine Design and Research Institute of China (MARIC) on Thursday (3 September) have secured Approval in Principle (AiP) for a new 114,000 DWT product and crude oil tanker designed to accommodate future conversion to LNG, methanol or ammonia.

Announced at SMM 2026, the concept addresses one of the biggest investment challenges facing shipping today: the need to develop vessels and capabilities that can support a range of alternative fuel options and pathways as technologies, infrastructure and regulations evolve.

While LNG is already a mature fuel pathway, methanol and ammonia remain at an earlier stage of development, with questions around global fuel availability, infrastructure development, economics and long-term adoption.

The 114,000 DWT tanker concept has been designed as a product and crude oil carrier that can accommodate future conversion to LNG, methanol or ammonia as technologies, regulations and fuel supply chains mature. By incorporating conversion readiness at the design stage, the concept aims to reduce future retrofit complexity and provide owners with greater confidence when planning long-term fleet investments.

The design concept was reviewed against LR’s July 2026 class rules and regulations, including requirements relating to ships using gases and other low-flashpoint fuels, alongside relevant IACS Common Structural Rules for oil tankers. Final classification and statutory approval remain subject to full compliance with all applicable rules and regulations.

Theo Kourmpelis, Global Business Director for Tankers, Lloyd’s Register, said: “Shipowners are being asked to make major investment decisions today despite continued uncertainty around which fuels will dominate in the decades ahead. Alternative fuel solutions each offer potential pathways to compliance, but fuel infrastructure, regulation and economics continue to evolve at different speeds around the world.

“Designs that preserve flexibility will be critical in helping owners manage risk while preparing for multiple future scenarios.”

Si Nan, Marine & Offshore Marketing Department Vice Director, MARIC, said: “As the industry explores different decarbonisation pathways, shipowners need vessel designs that can adapt alongside technological and regulatory developments. This concept was developed specifically to provide greater fuel flexibility and long-term resilience, allowing owners to respond to changing market requirements without being locked into a single fuel strategy.

“Receiving Approval in Principle from Lloyd’s Register is an important milestone that validates the design concept and supports its future development.”

 

Photo credit: Lloyd’s Register
Published: 4 September, 2026

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Alternative Fuels

DNV: Alternative-fuelled vessel orders hit highest monthly level since October 2024

LNG-fuelled vessels accounted for the vast majority of August activity while the strong summer performance marked a significant acceleration in ordering activity after a relatively slow start to the year.

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DNV: Alternative-fuelled vessel orders hit highest monthly level since October 2024

Latest data from classification society DNV’s Alternative Fuels Insight (AFI) platform alternative-fuelled vessel ordering was strong in August, with 52 new vessels added to the platform.

This is the highest monthly total since October 2024 and follows another active month in July, when 47 vessels were added to the database.

LNG-fuelled vessels accounted for the vast majority of August activity, with 46 orders recorded. The container segment led the way with 30 orders, while the car carrier segment contributed a further 12 LNG-fuelled vessels. In addition, four ethanol-fuelled bulk carriers and two hydrogen-powered bulk carriers were added during the month, as well as one LNG bunker vessel.

The strong summer performance marked a significant acceleration in ordering activity after a relatively slow start to the year. In total, 242 alternative-fuelled vessel orders have been placed in the first eight months of 2026, representing a 27% increase compared with the same period in 2025.

LNG remains the dominant fuel choice, accounting for 63% of all alternative-fuelled vessel orders registered so far this year. Container vessels represent the largest share of these LNG orders (59%), followed by car carriers (30%).

Jason Stefanatos, Global Decarbonization Director at DNV Maritime, said: “The past two months have been particularly strong for alternative-fuelled vessel ordering, with August recording the highest monthly total we’ve seen since October 2024. This has helped lift year-to-date orders to a level well above the same period last year.

“LNG remains the leading fuel choice, driven largely by activity in the container and car carrier segments. These sectors have been among the earliest adopters of alternative fuels, supported by predictable liner operations and increasing demand from cargo owners to reduce emissions across supply chains. 

“For many owners, LNG offers a combination of emissions reductions, fuel availability and future flexibility while the longer-term fuel landscape continues to evolve. 

“At the same time, the latest figures include orders for ethanol- and hydrogen-fuelled vessels, highlighting that owners continue to explore a range of decarbonization pathways. Different segments are making different fuel choices, but the overall level of activity demonstrates continued investment in lower-emission shipping.”

Screenshot 2026 09 04 at 12.29.26 PM Screenshot 2026 09 04 at 12.29.36 PM

 

Photo credit: DNV
Published: 4 September, 2026

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